Shielding Tape With Features For Mitigating Micro-Fractures And The Effects Thereof

ABSTRACT

In an electronic cable, a shielding tape prevents and mitigates the creation and propagation of micro-fractures and the deleterious effects thereof. In some embodiments, the shielding tape has layers which are oriented in a non-zero transverse relation with respect to each other, or have been treated to have non-zero orientations. Other embodiments include micro-fracture propagation mitigation means, such as perforations, ridges, waffling, and dimpling. In some embodiments, the layers of the shielding tape are bonded to each other with an electrically-conductive elastomeric adhesive. In other embodiments, the shielding tape is wrapped around a cable&#39;s dielectric and form an overlap gap, which is filled by an electrically-conductive elastomeric adhesive.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/621,901, filed Jan. 25, 2018, and it also claims the benefit of U.S.Provisional Application No. 62/621,905, filed Jan. 25, 2018, both ofwhich are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to electronic devices, and moreparticularly to shielding tape used in various cabled communicationproducts including coaxial cable, HDMI cable, power cords, Ethernetcables, and other electronic cables and devices.

BACKGROUND OF THE INVENTION

Electronic devices and components used in and around homes andbusinesses produce ingress noise affecting radio-frequency (“RF”)signals transmitted through nearby coaxial cables. Ingress noise can becaused by manufacturing or installation defects, by imperfections invarious electronic devices or components or electronic cables, and bypoor or inadequate shielding. Conventional shielding that may have oncebeen adequate is becoming less and less effective with the continuingproliferation of electronic devices. Communication in the 5G bandcreates particularly insidious noise issues. Ingress noise has become aserious problem impacting signal quality in television, voice, security,and broadband services.

Shielding is used in a variety of electronic cables and devices toreduce outside electrical interference or noise that could affect an RFsignal travelling through the cable or other device. The shielding alsohelps prevent the signal from radiating from the cable or other deviceand then interfering with other devices.

Conventionally, one type of shielding includes two or three shieldinglayers of aluminum or other shielding material (such as silver, copper,or Mu-metal) wherein each shielding layer of a laminated assembly isseparated by a separating layer, such as a plastic, e.g., polyethyleneterephthalate (“PET”), or a polyolefin such as polypropylene (“PP”).This type of shielding that combines layers of shielding material andseparating layers is often referred to as either “foil,” “laminatedtape,” “shielding tape,” “shielding laminate tape,” “laminated shieldingtape” (LST), and combinations or variations thereof. In some cables,such as coaxial cables, multiple layers of shielding tape (each of whichhas one or more shielding layers) are employed in the cable. Forexample, “tri-shield” cables include an inner foil surrounded by abraid, which is in turn surrounded by an outer foil. “Quad-shield”cables include an inner foil surrounded by an inner braid, which is inturn surrounded by an outer foil, in turn surrounded by an outer braid.

Multiple layers of shielding tape, while providing better shieldingperformance, also add to the cost and complexity of producing thecabling. Conventional shielding tape, with only one or two shieldinglayers, is susceptible to the formation of micro-fractures ormicro-cracks as the cable bends and flexes over time. Suchmicro-fractures are shown in FIGS. 1A and 1B. Micro-fractures may alsobe caused by the application of heat and stress to shielding tape,during the manufacturing process of a coaxial cable, as the tape isbonded to or applied over inner components of the cable such as thedielectric material. These micro-fractures and micro-cracks will allowRF signal ingress and egress. A way to mitigate the formation of themicro-fractures and micro-cracks, or a way to mitigate their effects, isneeded.

SUMMARY OF THE INVENTION

In an electronic cable, a shielding tape prevents and mitigates thecreation and propagation of micro-fractures and the deleterious effectsthereof. In some embodiments, the shielding tape has layers which areoriented in a non-zero transverse relation with respect to each other,or have been treated to have non-zero orientations. Other embodimentsinclude micro-fracture propagation mitigation means, such asperforations, ridges, waffling, and dimpling. In some embodiments, thelayers of the shielding tape are bonded to each other with anelectrically-conductive elastomeric adhesive. In other embodiments, theshielding tape is wrapped around a cable's dielectric and form anoverlap gap, which is filled by an electrically-conductive orelastomeric adhesive.

The above provides the reader with a very brief summary of someembodiments discussed below. Simplifications and omissions are made, andthe summary is not intended to limit or define in any way the scope ofthe invention or key aspects thereof. Rather, this brief summary merelyintroduces the reader to some aspects of the invention in preparationfor the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings:

FIGS. 1A and 1B are photographs of micro-fractures in electronic cables;

FIG. 1C is an electronic cable with a shielding tape;

FIG. 2A is a diagram of two layers of conventional shielding tape,illustrating RF noise egress through micro-fractures;

FIG. 2B is a diagram of two layers of a shielding tape, illustratingmitigation of RF noise egress through micro-fractures;

FIG. 3 is a diagram of two layers of a shielding tape, illustratingmitigation of RF noise egress through micro-fractures;

FIGS. 4A and 4B are diagrams of two bonded layers of conventionalshielding tape, illustrating RF noise egress through micro-fractures;

FIGS. 4C and 4D are diagrams of two elastomerically bonded layers ofshielding tape, illustrating the prevention of RF noise egress;

FIGS. 4E and 4F are diagrams of two elastomerically bonded layers ofshielding tape, illustrating the prevention of RF noise egress;

FIGS. 5A and 5B are diagrams of layers of shielding tape, at least oneof which is formed with micro-perforations;

FIGS. 6A and 6B are diagrams of a layer of conventional shielding tapedeveloping micro-fractures when placed under stress;

FIGS. 6C and 6D are diagrams of a layer of shielding tape with ridges,preventing the development of micro-fractures when placed under stress;

FIGS. 6E and 6F are diagrams of a layer of shielding tape with waffling,preventing the development of micro-fractures when placed under stress;

FIGS. 6G and 6H are diagrams of a layer of shielding tape with dimpling,preventing the development of micro-fractures when placed under stress;

FIG. 7A is a diagram of layers of shielding tape withelectrically-conductive adhesive disposed between the layers; and

FIGS. 7B and 7C are section and detailed views of a coaxial cable,showing electrically-conductive adhesive disposed within an overlap gapin shielding tape.

DETAILED DESCRIPTION

Reference now is made to the drawings, in which the same referencecharacters are used throughout the different figures to designate thesame elements. FIGS. 1A and 1B are optical microscope photographsshowing micro-fractures 10 formed through a shielding tape. Thesemicro-fractures 10 are elongate, longer than they are wide.Micro-fractures such as these allow RF ingress and egress.

FIG. 2A illustrates conventional laminated tape construction techniqueswhich might lead to the creation of such micro-fractures 10. FIG. 2Ashows two laminated tape layers 11 and 12. The layer 11 is an innerlayer and the layer 12 is an outer layer; the outer layer 12 surroundsthe inner layer 11. Though one having ordinary skill in the art shouldunderstand, discussion of conventional coaxial cable construction isdiscussed here for the purpose of context. This discussion is not meantto limit this entire disclosure to coaxial cables; indeed, thisdisclosure applies to other types of electronic cables and cords assuitable. Generally, most conventional coaxial cables have a centerconductor surrounded by a cylindrical dielectric. The dielectric is thenencircled by the shielding tape, which may include a foil layer, alaminated shielding tape layer, a braided layer, or a combinationthereof. Finally, an insulating jacket—generally a PVC jacket—surroundsthe entire assembly.

The layers 11 and 12 are two layers of the shielding tape in such aconventional coaxial cable. During the manufacturing processes of theselayers 11 and 12, rolling and stretching of the metal of the layers 11and 12 results in a generally longitudinal crystal orientation. Ifmicro-fractures later develop in the layers 11 and 12, suchmicro-fractures tend to be likewise oriented longitudinally. Wrappingthe layers 11 and 12 onto the cable can create or enlarge themicro-fractures. FIG. 2A shows two set of micro-fractures 13 and 14formed in the layers 11 and 12.

Frequently, micro-fractures propagate through the components of ashielding tape. This is what has occurred in FIG. 2A; it can be seenthat the micro-fractures 13 and 14 are registered with each other. Whenthe center conductor within the cable generates egress noise (indicatedthroughout these drawings by the reference character N), the noise N canpass through the micro-fractures 13 in the inner layer 11. When themicro-fractures 13 and 14 in both layers 11 and 12 are registered witheach other, however, the noise N will pass not only through the layer11, but also through the layer 12, thereby transmitting outside of thecable. It is noted that while the drawings generally show egress noise Nas a set of arrowed lines extending out of the cable, themicro-fractures are also vulnerable to ingress noise. Ingress noise isnot specifically discussed or shown here, but one having ordinary skillin the art will appreciate that it behaves similarly to egress noise Nwith respect to transmission through micro-fractures.

FIG. 1C illustrates a coaxial cable 110 constructed with shielding tapethat prevents and mitigates the formation and propagation ofmicro-fractures and also prevents and mitigates the deleterious effectsof RF signal ingress and egress through such micro-fractures. The cable110 has a center conductor 111, an insulating dielectric 112 surroundingthe conductor 111, a shielding tape 113 with these mitigation features,a flexible braid 114 encircling the shielding tape 113, and aninsulative jacket 115 surrounding everything.

The below construction methods, features, techniques, and structuresapply to the shielding tape 113, mitigate micro-fracture formation andpropagation, and also minimize RF signal ingress and egress. In general,improved shielding tapes are described which reduce the incidence,enlargement, and propagation of micro-fractures and micro-tears thatoften result from bending and flexing of cables and other devices. Thisnot only reduces signal egress or ingress but also improves the flexlife of the shielding tape, maintains electrical continuity, andminimizes performance degradation of the cable or other device overtime. Furthermore, outer shielding structures, such as braids, may beeliminated, thereby eliminating the need to remove such structures whenattaching a connector to the cable, and eliminating problems associatedwith outer shielding structures separating and interfering withconnector attachment.

FIG. 2B illustrates a construction technique which prevents thedevelopment of registered micro-fractures in the shielding tape used forshielding, and/or reduces the incidence of micro-fractures, andminimizes the dimensions of micro-fractures. The shielding tape shown inFIG. 2B is constructed with two separate metallic layers 20 and 21 inwhich some of the aluminum crystal orientation of one or more of theadjoining aluminum layers is at least partially biased by a surfacetreatment such as burnishing. It is briefly noted here that “aluminumlaminate” is sometimes used in this description to identify theshielding tape because aluminum is a common material choice for theshielding foil.

FIG. 2B shows micro-fractures 22 and 23 formed in the layers 20 and 21,respectively. As can be seen, the micro-fractures 22 and 23 are orientedtransversely with respect to each other. This is because the layers 20and 21 have been burnished differently. Burnishing is the process ofrubbing or smoothing the layers 20 and 21 in a certain direction byrepeatedly sliding a hard object tangentially in contact against thelayers 20 and 21. As burnishing continues, the crystals in the layers 20and 21 orient themselves consistently. This helps ensure that if amicro-fracture develops, it will develop along the orientation of thecrystals. In other words, when the crystals have acquired a consistentorientation the micro-fractures are predisposed to form along thatparticular orientation.

The inner layer 20 is burnished in a first direction arranging thecrystals into a first orientation (horizontal on the page), and theouter layer 21 is burnished in a second direction arranging the crystalsinto a second orientation (vertical on the page). FIG. 2B shows thefirst and second orientations generally as the direction of themicro-fractures 22 and 23, which are perpendicular to each other. Whilea perpendicular orientation may be preferable, any non-zero transverserelation is suitable. When the metallic layers 20 and 21 are joined toeach other (preferably with laminate between) during manufacturing toform the shielding tape for application to the cable, themicro-fractures 22 and 23 are offset; they have a non-zero transverseorientation with respect to each other. Therefore, longitudinal tearsare less likely to register with or near each other, and are thus morelikely to form only small holes through the shielding tape rather thanlong tears. In other words, overlapping micro-fractures 22 and 23 inadjacent layers 20 and 21 form small holes rather than tears, and smallholes allow less RF egress noise N to be emitted than do long tears.

While the construction technique shown in FIG. 2B does not necessarilyreduce the incidence of micro-fractures, it does reduce the transmissionof egress noise N by orienting the micro-fractures in an offset fashion.RF ingress and egress through the micro-fractures 22 and 23 is thusminimized, and shielding effectiveness is maintained despite thepresence of the micro-fractures 22 and 23 in the individual layers 20and 21.

FIG. 3 illustrates another shielding tape construction technique. Twometallic layers 30 and 31 of the shielding tape each have opposed ends32 and 33 and opposed sides 34 and 35. They also have a similar aluminumcrystal orientation, namely, between the sides 34 and 35. This crystalorientation is created by burnishing or some other technique. The knownconsistent orientation of aluminum crystals is exploited to mitigateegress noise N transmission. Before the metallic layers 30 and 31 arejoined to form the shielding tape, one of the layers 30 or 31 is rotatedwith respect to the other. FIG. 3B shows the outer layer 31 offset andgenerally perpendicular to the inner layer 30. While a perpendicularoffset orientation may be preferable, any non-zero transverse relationis suitable. The layers 30 and 31 are then joined.

By offsetting or orienting the layers 30 and 31 transversely withrespect to each other, shielding loss from micro-fractures is minimized.While the micro-fractures 36 and 37 may overlap with each other, they donot register, and so they can only form small holes rather than longtears. Laminating two or more such layers 30 and 31, one of which hasbeen physically offset at any non-zero angle up to and including ninetydegrees prior to lamination, minimizes the dimensions of the openingthrough which any RF ingress or egress can occur and thereby reduces thepotential for RF signal ingress or egress through a micro-fracture ofthe aluminum layer.

In another method, each layer of the shielding tape is annealed prior tolamination. Under appropriate annealing procedures, aluminum crystalgrain size is reduced and orientation of the crystals is randomized. Ifmicro-fractures later occur in the presence of smaller grains andrandomized crystal orientation, such micro-fractures are less likely tobe parallel with or coterminous with a micro-fracture in an adjoininglayer. Thus, a channel through which any ingress or egress noise mustpenetrate, if any such channel exists, is greatly reduced in size.Shielding from RF signal ingress or egress is thereby preserved.

Conventionally, the components of the shielding tape 40 are joined toeach other with a non-elastomeric adhesive, as shown in FIG. 4A. When astress is applied on the shielding tape 40, such as a shear stress 41,micro-fractures 42 will develop in one or both of the layers, and egressnoise N will transmit through these micro-fractures 42.

FIGS. 4C and 4D show three laminated layers 50, 51, and 52 of ashielding tape with an adhesive 53 disposed therebetween. The adhesive53 has elastomeric properties and thus permits flexing without theconsequential forming of micro-fractures in the layers 50, 51, or 52.The elasticity of the adhesive 53 reduces the transmission from onelayer to another of the stresses caused by bending or flexing, therebydecreasing the likelihood of the development of a micro-fracture. But,if such a micro-fracture does occur in one aluminum layer despite theelasticity of the bonding adhesive, there is less likelihood thatparallel or coterminous micro-fractures will propagate or develop in theadjoining layers, and there is a greater likelihood that anymicro-fracture present in one layer will be covered by or adjacent to anundamaged segment of the adjacent layer.

The adhesive 53 is applied across the entire surface of each layer 50,51, and 52, so that bonding between two adjacent layers is made acrossthe entirety of abutting surfaces. The shielding tape is constructed inthis fashion and is then wrapped around the cable. While FIG. 4D doesillustrates three layers 50, 51, and 52, it is noted that a greater orlesser number of layers may be used, depending on factors such as theperformance specifications, design constrictions, and budget of themanufacturer.

FIGS. 4E and 4F show an alternate embodiment of elastomeric bonding.There, the shielding tape is still constructed from three layers 50, 51,and 52, but the adhesive 53 is applied differently. The layers 50, 51,and 52 each have opposed ends 54 and 55 and opposed sides 56 and 57. Theadhesive 53, rather than being applied across an entire face of thelayer, is only applied along the sides 56 and 57. No adhesive 53 isapplied between the sides 56 and 57. In some embodiments, adhesive 53 isapplied along the opposed ends 55 and 56.

In applications involving coaxial cable, the shielding tape is commonlymanufactured in long strips, so in this particular application thebonding adhesive is preferably applied only along the longitudinal sides56 and 57 of the layers 50, 51 and 52. Flexibility of unbonded sectionsof the layers 50, 51, and 52, between the sides 56 and 57, provides ameasure of stress relief that reduces the likelihood of micro-fracturedevelopment in the layers 50, 51, and 52. FIGS. 4E and 4F show theapplication of the bonding adhesive only along the sides 56 and 57 ofthe layers 50, 51, and 52. When the shear stress 41 is applied,micro-fractures do not develop. Other patterns of adhesive placement maybe suitable or preferable in some applications.

The above construction techniques mitigate the effects of micro-fractureincidence and propagation. Other construction techniques directlymitigate the incidence and propagation of micro-fractures. Thesemicro-fracture propagation mitigation means or features are formed inthe metallic layer of the shielding and include perforations ormicro-perforations (FIGS. 5A and 5B), ridges (FIGS. 6C and 6D), waffling(FIGS. 6E and 6F), and dimpling (FIGS. 6G and 6H).

One such means of reducing the incidence of micro-fractures is with theuse of an array of perforations or micro-perforations, as shown in FIGS.5A and 5B, which show a shielding tape 60 under no stress and undershear stress 41. In this embodiment, an array of micro-perforations 61is applied to one or more layers 62, 63, or 64 of the shielding tape 60.Such micro-perforations 61 in a layer alleviate any stresses present anddecreases the likelihood that any such stresses will cause amicro-fracture. Moreover, where stresses do cause a micro-fracture, suchmicro-perforations 61 prevent and limit further expansion of themicro-fractures beyond the micro-perforation 61. The micro-perforationsthus act as a stop to migration or extension of micro-fractures acrossmore of the affected layer.

The micro-perforations 61 have a major dimension, which is the longestdistance between two edges of a micro-perforation. The major dimensionis smaller in dimension than the amplitude of the wavelength of the RFsignal to be carried by the particular cable in which the shielding tape60 is to be used. Thus, RF signals cannot pass through any one of theintact micro-perforations 61. Indeed, ingress or egress of noise fromdesired RF signals through a micro-perforation 61 can only occur in theevent that there is a tear at a micro-perforation. Even then, the noiseingress or egress can only pass entirely through the shielding tap 60 ifthe adjacent layers have also been torn at micro-perforations 61 whichare registered with the torn micro-perforation 61.

Because the micro-perforations 61 are very small, any ingress or egressof RF signals through the micro-perforations 61 is limited to muchhigher frequencies and smaller wavelengths than might otherwise leakthrough a larger micro-fracture. Moreover, noise ingress would be fromRF signals different in wavelength from those transmitted through thecable. In other words, use of an array of micro-perforations 61 isespecially suitable in applications where ingress or egress of higherfrequency range RF signals is not a significant consideration and can betolerated.

The shielding tape 60 shown in FIGS. 5A and 5B includes an array ofmicro-perforations 61 in which the micro-perforations 61 are arranged inrows, and the micro-perforations 61 in each row are offset horizontallyfrom those in the row above and below. The micro-perforations 61preferably have a circular shape, with their major dimension being thediameter of that circular shape, but in other embodiments may have othershapes whose major dimension is smaller than the wavelength of the RFnoise, especially of RF noise in the 5G spectrum. Preferably, the majordimension is smaller than approximately 12 millimeters to mitigate RFfrequencies around 24 GHz. More preferably, the major dimension issmaller than approximately 3.5 millimeters to mitigate RF frequenciesaround 86 GHz. Still more preferably, the major dimension is smallerthan approximately 3 millimeters to mitigate RF frequencies around 95GHz. In the array, the micro-perforations 61 are preferably spaced apartby at least the major dimension.

As can be seen in FIGS. 5A and 5B, the shielding tape 60 not only hasthe micro-perforations 61, but its layers 62, 63, and 64 are joined bythe elastomeric adhesive 53. When the shear stress 41 is applied, thelayers 62, 63, and 64 stretch along the direction of the shear stress41, the adhesive 53 elastically deforms, and the micro-perforations 61deform to acquire an elongated shape. When the shear stress 41 isreleased, the micro-perforations return to their original shape, as inFIG. 5A.

FIGS. 6A and 6B show a conventional laminated layer 70, both under nostress and under shear stress 41. As has been discussed, when alaminated layer 70 is placed under shear stress 41, micro-fractures 71will develop, generally transverse to the direction of the shear stress41. This allows egress noise N to transmit through the layer 70. Variousmethods of treating, aligning, orienting, and bonding layers has beendiscussed. The layers can also be textured in different ways.

FIGS. 6C and 6D illustrate a single laminated metallic layer 73 ofshielding tape, where the layer has a texture. The layer 73 is formedwith a plurality of corrugations or ridges 74. The layer 73 has opposedends 75 and 76 and opposed sides 77 and 78. Generally, the layer 73 isaligned along a plane P extending between the ends 75 and 76 and betweenthe sides 77 and 78. The ridges 74, extending between the sides 77 and78, project into and out of that plane. Each ridge 74 has a first wall80 and a second wall 81, meeting at a hinge point 82 therebetween. Thefirst and second walls 80 and 81 are generally straight and flat andoriented obliquely with respect to each other. The layer 73 has adimension A between the opposed ends 75 and 76. When the layer 73 isplaced under the shear stress 41, the layer 73 acquires a new dimensionA′. Generally, because that shear stress 41 will be positive to act toextend the layer 73, the dimension A′ is greater than the dimension A.However, in some cases, the shear stress 41 will be negative and willcause the ends 75 and 76 to collapse toward each other, in which casethe dimension A′ will be less than the dimension A. When the layer 73 isunder a positive shear stress 41, the ridges 74 respond by flatteningand lengthening. This accommodates the effect of the shear stress 41 tostretch the layer 73. Without such accommodation, the layer 73 wouldtend to tear and develop micro-fractures. In other words, the ridges 74prevent or mitigate the development of micro-fractures.

The layer 73 is suitable for use as the sole layer in a shielding tape,or it may be used without similar layers 73, or with other differentlayers discussed herein, in different orientations described herein andwith different surface treatments described herein.

FIGS. 6E and 6F show a metallic layer 84 of a shielding tape withwaffling 85 formed by intersecting ridges 86 separated and spaced apartby depressions 87. The ridges 86 are oriented normally with respect to aplane in which the layer 84 lies, and there are two sets of ridges 86:one set which is aligned vertically, or end-to-end, and another setwhich is aligned horizontally, or side-to-side, so that the two sets ofridges are transverse and preferably perpendicular with respect to eachother across both sides of the layer 84. The ridges 86 project normallyto the layer 84, both in front of and behind the layer 84, and thedepressions 87 are disposed between the ridges 86.

The ridges 86 are reinforced portions of the layer 84, representing athickened portion of the layer 84, while the depressions 87 are“thinned” portions, in that they are thinner than the ridges 86, but arestill generally as thick as the other layers, such as layers 50, 51, 52,70, etc. When the shear stress is applied to the layer 84 and itstretches, the ridges 86 respond by stretching slightly, and thedepressions 87 respond by stretching slightly. Should a micro-fractureoccur, it generally forms in the thinned area of a depression 87, and itis limited to the depression 87 in which it forms; it is unlikely topropagate through a ridge 86 to an adjacent depression 87. As such, thelayer 84 prevents and mitigates the development of micro-fractures.

The layer 84 is suitable for use as the sole layer in a shielding tape,or it may be used without similar layers 84, or with other differentlayers discussed herein, in different orientations described herein andwith different surface treatments described herein.

FIGS. 6G and 6H show another metallic layer 90 of a shielding tape witha plurality of dimples or concavities 91 formed therein and arranged inan array. These concavities 91 alleviate any stresses present anddecrease the likelihood that stresses will cause a micro-fracture.Moreover, where stresses do cause a micro-fracture, such concavities 91prevent and limit further expansion of the micro-fractures beyond theconcavity 91. The concavities 91 thus act as a stop to migration orextension of micro-fractures across more of the layer 90.

Each concavity 91 is a semi-spherical concave depression, extending intothe body of the layer 90. The concavities 91 all have a major dimensioncorresponding to the diameter of the semi-spherical depression. In thearray of concavities 91 in the layer 90, the concavities 91 are arrangedin rows, and the concavities 91 in each row are offset horizontally fromthose in the row above and below. The concavities 91 are preferably butnot necessarily spaced apart by at least the major dimension. Theconcavities 91 preferably have a circular shape, with their majordimension being a diameter, but in other embodiments may have othershapes. When the shear stress 41 is applied, the layer 90 stretchesalong the direction of the shear stress 41 and the concavities 91deform. Because the concavities 91 are semi-spherical, they can expand.They have more surface area than their cross-sectional circular outlinecircumscribes, and that surface area is stretched out when the layer 90stretches under the shear stress 41. When the shear stress 41 isreleased, the concavities 91 return to their original shape, as in FIG.6G.

The layer 90 is suitable for use as the sole layer in a shielding tape,or it may be used without similar layers 90, or with other differentlayers discussed herein, in different orientations described herein andwith different surface treatments described herein.

As noted above, an elastomeric adhesive may be used between layers ofthe shielding tape. The elastomeric adhesive has elastomericcharacteristics. The adhesive may be alternately formulated, however, toinclude metallic solids. An adhesive containing metallic solids may beelastomeric or non-elastomeric.

In FIG. 7A, three layers 94, 95, and 96 are shown, each with anelectrically-conductive adhesive 97 disposed between. The adhesive 97preferably but not necessarily includes the elastomeric adhesive 98 andsmall metallic solids 99 dispersed throughout the adhesive 98. In someembodiments, the adhesive 97 includes the metallic solids 99 and anon-elastomeric adhesive 98. The metallic solids 99 include aluminum,nickel, copper, carbon, graphene, or other like metals having goodelectrical conductivity properties, and range in size as small as only afew microns, such as just two or three microns in dimension, though theyare illustrated in these drawings as much bigger for clarity only. Themetallic solids 99 are homogenously dispersed and have a high densitywithin the adhesive 97 to prevent transmission of very high frequency RFingress or egress signals, and the conductivity (and thus noisemitigation properties) of the adhesive 97 improves with greater densityof metallic solids 99 through quantum tunneling effects. RF signal ornoise ingress or egress through the adhesive bond between the layers 94,95, and 96 is effectively minimized by means of the electricallyconductive adhesive 97. The dispersion of metallic solids 99 in theadhesive 97 enhances shielding effectiveness, and the adhesive 97 itselfis thereby made to serve as a barrier to RF signals, sometimes withoutthe need for an additional layer of laminate material or metallic layer.If or where micro-fractures develop in the layers 94, 95, and 96, theelectrically-conductive adhesive 97 mitigates the transmission of egressnoise N.

The electrically-conductive adhesive 97 is used in another context aswell. FIGS. 7B and 7C illustrate an exemplary electronic cable 100having a center conductor 101, a dielectric insulator 102 surroundingthe center conductor 101, and shielding tape 103 wrapped around theinsulator 102. The shielding tape 103 has opposed edges 104 and 105. Theedges 104 and 105 overlap slightly to form an overlap gap 106. Theelectrically-conductive adhesive 97 is disposed in this overlap gap 106.The adhesive 97, dispersed with metallic solids 99, bonds the edges 104and 105 to each other to prevent the shielding tape 103 from separating.However, the electrically-conductive adhesive 97 also prevents the gap106 from becoming a tunnel for RF signal or noise ingress and egress.

It is noted that these methods, features, structures, and constructiontechniques can be combined. For example, the shielding tape 113 of FIG.1C may have a layer with waffling, that layer may be elastomericallybonded at the edges, and an electrically-conductive adhesive may be usedwithin an overlap gap when the shielding tape 113 is wrapped around thedielectric 112. Other combinations of the above mitigation features arecontemplated as well.

A preferred embodiment is fully and clearly described above so as toenable one having skill in the art to understand, make, and use thesame. Those skilled in the art will recognize that modifications may bemade to the description above without departing from the spirit of theinvention, and that some embodiments include only those elements andfeatures described, or a subset thereof. To the extent thatmodifications do not depart from the spirit of the invention, they areintended to be included within the scope thereof.

The invention claimed is:
 1. Shielding tape in an electronic cable, theshielding tape comprising: a metallic layer; and micro-fracturepropagation mitigation means formed in the metallic layer.
 2. Theshielding tape of claim 1, wherein the micro-fracture propagationmitigations means includes perforations formed through the metalliclayer.
 3. The shielding tape of claim 2, wherein the perforations have amajor dimension smaller than approximately 12 millimeters.
 4. Theshielding tape of claim 3, wherein the major dimension is smaller thanapproximately 3 millimeters.
 5. The shielding tape of claim 2, whereinthe perforations are spaced apart in an array across the metallic layer.6. The shielding tape of claim 5, wherein the perforations have a majordimension smaller than approximately 12 millimeters and are spaced apartfrom each other in the array by at least the major dimension.
 7. Theshielding tape of claim 6, wherein the major dimension is smaller thanapproximately 3 millimeters.
 8. The shielding tape of claim 1, whereinthe micro-fracture propagation mitigations means includes ridges formedin the metallic layer.
 9. The shielding tape of claim 8, wherein: eachridge in the metallic layer comprises a first wall and a second wallarranged obliquely with respect to the first wall; and the first andsecond walls each project into and out of a plane along which themetallic layer extends.
 10. The shielding tape of claim 1, wherein themicro-fracture propagation mitigations means includes waffling formed inthe metallic layer.
 11. The shielding tape of claim 10, wherein thewaffling is formed by intersecting ridges on the metallic layer spacedapart by depressions between the ridges.
 12. The shielding tape of claim1, wherein the micro-fracture propagation mitigations means includesdimpling formed in the metallic layer.
 13. The shielding tape of claim12, wherein the dimpling is formed by semi-spherical concave depressionsinto the layer.
 14. The shielding tape of claim 13, wherein the concavedepressions are spaced apart in an array across the metallic layer. 15.The shielding tape of claim 14, wherein the concave depressions eachhave a major dimension, and the concave depressions are spaced apartfrom each other in the array by at least the major dimension. 16.Shielding tape in an electronic cable, the shielding tape comprising: afirst metallic layer having a first orientation along whichmicro-fractures are predisposed to form; a second metallic layer havinga second orientation along which micro-fractures are predisposed toform; and the first and second orientations have a non-zero transverserelation with respect to each other.
 17. The shielding tape of claim 16,wherein the first and second orientations in the first and secondmetallic layers are formed by burnishing the first and second metalliclayers.
 18. The shielding tape of claim 16, wherein the first metalliclayer is arranged with a non-zero transverse orientation with respect tothe second metallic layer.
 19. Shielding tape in an electronic cable,the shielding tape comprising: a first layer; a second layer; anadhesive disposed between the first and second layers; and metallicsolids dispersed throughout the adhesive, defining the adhesive withelectrically conductive material characteristics.
 20. The shielding tapeof claim 19, wherein the adhesive is an elastomeric adhesive.
 21. Anelectronic cable comprising: a conductor; an insulator surrounding theconductor; shielding tape wrapped around the insulator, the shieldingtape having overlapping edges forming an overlap gap therebetween; anadhesive disposed in the overlap gap; and metallic solids dispersedthroughout the adhesive, defining the adhesive with electricallyconductive material characteristics.
 22. The cable of claim 21, whereinthe adhesive is an elastomeric adhesive.